1
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Oda M. Analysis of the Structural Dynamics of Proteins in the Ligand-Unbound and -Bound States by Diffracted X-ray Tracking. Int J Mol Sci 2023; 24:13717. [PMID: 37762021 PMCID: PMC10531450 DOI: 10.3390/ijms241813717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 09/03/2023] [Accepted: 09/05/2023] [Indexed: 09/29/2023] Open
Abstract
Although many protein structures have been determined at atomic resolution, the majority of them are static and represent only the most stable or averaged structures in solution. When a protein binds to its ligand, it usually undergoes fluctuation and changes its conformation. One attractive method for obtaining an accurate view of proteins in solution, which is required for applications such as the rational design of proteins and structure-based drug design, is diffracted X-ray tracking (DXT). DXT can detect the protein structural dynamics on a timeline via gold nanocrystals attached to the protein. Here, the structure dynamics of single-chain Fv antibodies, helix bundle-forming de novo designed proteins, and DNA-binding proteins in both ligand-unbound and ligand-bound states were analyzed using the DXT method. The resultant mean square angular displacements (MSD) curves in both the tilting and twisting directions clearly demonstrated that structural fluctuations were suppressed upon ligand binding, and the binding energies determined using the angular diffusion coefficients from the MSD agreed well with the binding thermodynamics determined using isothermal titration calorimetry. In addition, the size of gold nanocrystals is discussed, which is one of the technical concerns of DXT.
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Affiliation(s)
- Masayuki Oda
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, 1-5 Hangi-cho, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan
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2
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Structural Comparison of Human Anti-HIV-1 gp120 V3 Monoclonal Antibodies of the Same Gene Usage Induced by Vaccination and Chronic Infection. J Virol 2018; 92:JVI.00641-18. [PMID: 29997214 DOI: 10.1128/jvi.00641-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 06/30/2018] [Indexed: 01/01/2023] Open
Abstract
Elucidating the structural basis of antibody (Ab) gene usage and affinity maturation of vaccine-induced Abs can inform the design of immunogens for inducing desired Ab responses in HIV vaccine development. Analyses of monoclonal Abs (MAbs) encoded by the same immunoglobulin genes at different stages of maturation can help to elucidate the maturation process. We have analyzed four human anti-V3 MAbs with the same VH1-3*01 and VL3-10*01 gene usage. Two MAbs, TA6 and TA7, were developed from a vaccinee in the HIV vaccine phase I trial DP6-001 with a polyvalent DNA prime/protein boost regimen, and two others, 311-11D and 1334, were developed from HIV-infected patients. The somatic hypermutation (SHM) rates in VH of vaccine-induced MAbs are lower than in chronic HIV infection-induced MAbs, while those in VL are comparable. Crystal structures of the antigen-binding fragments (Fabs) in complex with V3 peptides show that these MAbs bind the V3 epitope with a new cradle-binding mode and that the V3 β-hairpin lies along the antigen-binding groove, which consists of residues from both heavy and light chains. Residues conserved from the germ line sequences form specific binding pockets accommodating conserved structural elements of the V3 crown hairpin, predetermining the Ab gene selection, while somatically mutated residues create additional hydrogen bonds, electrostatic interactions, and van der Waals contacts, correlating with an increased binding affinity. Our data provide a unique example of germ line sequences determining the primordial antigen-binding sites and SHMs correlating with affinity maturation of Abs induced by vaccine and natural HIV infection.IMPORTANCE Understanding the structural basis of gene usage and affinity maturation for anti-HIV-1 antibodies may help vaccine design and development. Antibodies targeting the highly immunogenic third variable loop (V3) of HIV-1 gp120 provide a unique opportunity for detailed structural investigations. By comparing the sequences and structures of four anti-V3 MAbs at different stages of affinity maturation but of the same V gene usage, two induced by vaccination and another two by chronic infection, we provide a fine example of how germ line sequence determines the essential elements for epitope recognition and how affinity maturation improves the antibody's recognition of its epitope.
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3
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Jeliazkov JR, Sljoka A, Kuroda D, Tsuchimura N, Katoh N, Tsumoto K, Gray JJ. Repertoire Analysis of Antibody CDR-H3 Loops Suggests Affinity Maturation Does Not Typically Result in Rigidification. Front Immunol 2018; 9:413. [PMID: 29545810 PMCID: PMC5840193 DOI: 10.3389/fimmu.2018.00413] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 02/14/2018] [Indexed: 12/18/2022] Open
Abstract
Antibodies can rapidly evolve in specific response to antigens. Affinity maturation drives this evolution through cycles of mutation and selection leading to enhanced antibody specificity and affinity. Elucidating the biophysical mechanisms that underlie affinity maturation is fundamental to understanding B-cell immunity. An emergent hypothesis is that affinity maturation reduces the conformational flexibility of the antibody's antigen-binding paratope to minimize entropic losses incurred upon binding. In recent years, computational and experimental approaches have tested this hypothesis on a small number of antibodies, often observing a decrease in the flexibility of the complementarity determining region (CDR) loops that typically comprise the paratope and in particular the CDR-H3 loop, which contributes a plurality of antigen contacts. However, there were a few exceptions and previous studies were limited to a small handful of cases. Here, we determined the structural flexibility of the CDR-H3 loop for thousands of recent homology models of the human peripheral blood cell antibody repertoire using rigidity theory. We found no clear delineation in the flexibility of naïve and antigen-experienced antibodies. To account for possible sources of error, we additionally analyzed hundreds of human and mouse antibodies in the Protein Data Bank through both rigidity theory and B-factor analysis. By both metrics, we observed only a slight decrease in the CDR-H3 loop flexibility when comparing affinity matured antibodies to naïve antibodies, and the decrease was not as drastic as previously reported. Further analysis, incorporating molecular dynamics simulations, revealed a spectrum of changes in flexibility. Our results suggest that rigidification may be just one of many biophysical mechanisms for increasing affinity.
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Affiliation(s)
- Jeliazko R Jeliazkov
- Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD, United States
| | - Adnan Sljoka
- Department of Informatics, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo, Japan
| | - Daisuke Kuroda
- Department of Bioengineering, School of Engineering, The University of Tokyo, Tokyo, Japan.,Medical Device Development and Regulation Research Center, School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Nobuyuki Tsuchimura
- Department of Informatics, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo, Japan
| | - Naoki Katoh
- Department of Informatics, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo, Japan
| | - Kouhei Tsumoto
- Department of Bioengineering, School of Engineering, The University of Tokyo, Tokyo, Japan.,Laboratory of Medical Proteomics, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Jeffrey J Gray
- Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD, United States.,Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, United States.,Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD, United States.,Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, United States
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4
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Mishra AK, Mariuzza RA. Insights into the Structural Basis of Antibody Affinity Maturation from Next-Generation Sequencing. Front Immunol 2018; 9:117. [PMID: 29449843 PMCID: PMC5799246 DOI: 10.3389/fimmu.2018.00117] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 01/15/2018] [Indexed: 12/26/2022] Open
Abstract
Affinity maturation is the process whereby the immune system generates antibodies of higher affinities during a response to antigen. It is unique in being the only evolutionary mechanism known to operate on a molecule in an organism's own body. Deciphering the structural mechanisms through which somatic mutations in antibody genes increase affinity is critical to understanding the evolution of immune repertoires. Next-generation sequencing (NGS) has allowed the reconstruction of antibody clonal lineages in response to viral pathogens, such as HIV-1, which was not possible in earlier studies of affinity maturation. Crystal structures of antibodies from these lineages bound to their target antigens have revealed, at the atomic level, how antibodies evolve to penetrate the glycan shield of envelope glycoproteins, and how viruses in turn evolve to escape neutralization. Collectively, structural studies of affinity maturation have shown that increased antibody affinity can arise from any one or any combination of multiple diverse mechanisms, including improved shape complementarity at the interface with antigen, increased buried surface area upon complex formation, additional interfacial polar or hydrophobic interactions, and preorganization or rigidification of the antigen-binding site.
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Affiliation(s)
- Arjun K Mishra
- W. M. Keck Laboratory for Structural Biology, Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Rockville, MD, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, College Park, MD, United States
| | - Roy A Mariuzza
- W. M. Keck Laboratory for Structural Biology, Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Rockville, MD, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, College Park, MD, United States
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5
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Cersosimo U, Sgorbissa A, Foti C, Drioli S, Angelica R, Tomasella A, Picco R, Semrau MS, Storici P, Benedetti F, Berti F, Brancolini C. Synthesis, Characterization, and Optimization for in Vivo Delivery of a Nonselective Isopeptidase Inhibitor as New Antineoplastic Agent. J Med Chem 2015; 58:1691-704. [DOI: 10.1021/jm501336h] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Ulma Cersosimo
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via Giorgieri 1, 34127 Trieste, Italy
| | - Andrea Sgorbissa
- Dipartimento
di Scienze Mediche e Biologiche, Università degli Studi di Udine, P.le Kolbe 4, 33100 Udine, Italy
| | - Carmen Foti
- Dipartimento
di Scienze Mediche e Biologiche, Università degli Studi di Udine, P.le Kolbe 4, 33100 Udine, Italy
| | - Sara Drioli
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via Giorgieri 1, 34127 Trieste, Italy
| | - Rosario Angelica
- Dipartimento
di Scienze Mediche e Biologiche, Università degli Studi di Udine, P.le Kolbe 4, 33100 Udine, Italy
| | - Andrea Tomasella
- Dipartimento
di Scienze Mediche e Biologiche, Università degli Studi di Udine, P.le Kolbe 4, 33100 Udine, Italy
| | - Raffaella Picco
- Dipartimento
di Scienze Mediche e Biologiche, Università degli Studi di Udine, P.le Kolbe 4, 33100 Udine, Italy
| | - Marta Stefania Semrau
- Structural
Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Area
Science Park, 34149 Basovizza, Trieste, Italy
| | - Paola Storici
- Structural
Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Area
Science Park, 34149 Basovizza, Trieste, Italy
| | - Fabio Benedetti
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via Giorgieri 1, 34127 Trieste, Italy
| | - Federico Berti
- Dipartimento
di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via Giorgieri 1, 34127 Trieste, Italy
| | - Claudio Brancolini
- Dipartimento
di Scienze Mediche e Biologiche, Università degli Studi di Udine, P.le Kolbe 4, 33100 Udine, Italy
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6
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Crystal structure of two anti-porphyrin antibodies with peroxidase activity. PLoS One 2012; 7:e51128. [PMID: 23240001 PMCID: PMC3519839 DOI: 10.1371/journal.pone.0051128] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 10/30/2012] [Indexed: 01/07/2023] Open
Abstract
We report the crystal structures at 2.05 and 2.45 Å resolution of two antibodies, 13G10 and 14H7, directed against an iron(III)-αααβ-carboxyphenylporphyrin, which display some peroxidase activity. Although these two antibodies differ by only one amino acid in their variable λ-light chain and display 86% sequence identity in their variable heavy chain, their complementary determining regions (CDR) CDRH1 and CDRH3 adopt very different conformations. The presence of Met or Leu residues at positions preceding residue H101 in CDRH3 in 13G10 and 14H7, respectively, yields to shallow combining sites pockets with different shapes that are mainly hydrophobic. The hapten and other carboxyphenyl-derivatized iron(III)-porphyrins have been modeled in the active sites of both antibodies using protein ligand docking with the program GOLD. The hapten is maintained in the antibody pockets of 13G10 and 14H7 by a strong network of hydrogen bonds with two or three carboxylates of the carboxyphenyl substituents of the porphyrin, respectively, as well as numerous stacking and van der Waals interactions with the very hydrophobic CDRH3. However, no amino acid residue was found to chelate the iron. Modeling also allows us to rationalize the recognition of alternative porphyrinic cofactors by the 13G10 and 14H7 antibodies and the effect of imidazole binding on the peroxidase activity of the 13G10/porphyrin complexes.
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7
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Debler EW, Kaufmann GF, Kirchdoerfer RN, Mee JM, Janda KD, Wilson IA. Crystal structures of a quorum-quenching antibody. J Mol Biol 2007; 368:1392-402. [PMID: 17400249 PMCID: PMC1994716 DOI: 10.1016/j.jmb.2007.02.081] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2006] [Revised: 02/17/2007] [Accepted: 02/27/2007] [Indexed: 01/28/2023]
Abstract
A large number of Gram-negative bacteria employ N-acyl homoserine lactones (AHLs) as signaling molecules in quorum sensing, which is a population density-dependent mechanism to coordinate gene expression. Antibody RS2-1G9 was elicited against a lactam mimetic of the N-acyl homoserine lactone and represents the only reported monoclonal antibody that recognizes the naturally-occuring N-acyl homoserine lactone with high affinity. Due to its high cross-reactivity, RS2-1G9 showed remarkable inhibition of quorum sensing signaling in Pseudomonas aeruginosa, a common opportunistic pathogen in humans. The crystal structure of Fab RS2-1G9 in complex with a lactam analog revealed complete encapsulation of the polar lactam moiety in the antibody-combining site. This mode of recognition provides an elegant immunological solution for tight binding to an aliphatic, lipid-like ligand with a small head group lacking typical haptenic features, such as aromaticity or charge, which are often incorporated into hapten design to generate high-affinity antibodies. The ability of RS2-1G9 to discriminate between closely related AHLs is conferred by six hydrogen bonds to the ligand. Conversely, cross-reactivity of RS2-1G9 towards the lactone is likely to originate from conservation of these hydrogen bonds as well as an additional hydrogen bond to the oxygen of the lactone ring. A short, narrow tunnel exiting at the protein surface harbors a portion of the acyl chain and would not allow entry of the head group. The crystal structure of the antibody without its cognate lactam or lactone ligands revealed a considerably altered antibody-combining site with a closed binding pocket. Curiously, a completely buried ethylene glycol molecule mimics the lactam ring and, thus, serves as a surrogate ligand. The detailed structural delineation of this quorum-quenching antibody will aid further development of an antibody-based therapy against bacterial pathogens by interference with quorum sensing.
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Affiliation(s)
- Erik W. Debler
- Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Gunnar F. Kaufmann
- Departments of Chemistry and Immunology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Robert N. Kirchdoerfer
- Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Jenny M. Mee
- Departments of Chemistry and Immunology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Kim D. Janda
- Departments of Chemistry and Immunology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
- The Worm Institute for Research and Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Ian A. Wilson
- Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
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8
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Scotti C, Gherardi E. Structural Basis of Affinity Maturation of the TEPC15/Vκ45.1 Anti-2-phenyl-5-oxazolone Antibodies. J Mol Biol 2006; 359:1161-9. [PMID: 16682055 DOI: 10.1016/j.jmb.2006.04.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2006] [Revised: 04/11/2006] [Accepted: 04/12/2006] [Indexed: 11/29/2022]
Abstract
Affinity maturation is a process that leads to the emergence of more efficient antibodies following initial antigen encounter and represents a key strategy of the adaptive immunity of vertebrate organisms. Earlier and detailed sequence studies of the antibody response to a model antigen, the hapten 2-phenyl-5-oxazolone (phOx), define three different classes of antibodies. Class I antibodies use the V(H)Ox1/V(kappa)Ox1 gene pair and dominate the early stages of the anti-phOx response, class II antibodies use the V(kappa)Ox1 gene but a different V(H) segment and are common in the intermediate stages, and class III antibodies use the TEPC15/V(kappa)45.1 genes and play the greatest role in the late stages. Only the crystal structure of one anti-phOx antibody, the class II NQ10/12.5 Fab fragment, has been described. Here we report the crystal structures of the scFv form of the low and high affinity anti-phOx class III antibodies NQ10/1.12 and NQ16/113.8 complexed with the hapten. The two antibodies differ by nine amino acid substitutions, all located in the V(H) domain. Analysis of the two structures shows that affinity maturation results from an increase in surface complementarity, as a consequence of a finely tuned and highly concerted process chaperoned by the somatic mutations, and implies a more efficient hapten-induced fit in the mature antibody. The data also demonstrate that class III antibodies respond in a completely different way to the architectural problem of binding phOx compared to the class II antibody NQ10/12.5.
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Affiliation(s)
- Claudia Scotti
- Dipartimento di Medicina Sperimentale, Universita' di Pavia, Italy.
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9
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Cho S, Swaminathan CP, Yang J, Kerzic MC, Guan R, Kieke MC, Kranz DM, Mariuzza RA, Sundberg EJ. Structural basis of affinity maturation and intramolecular cooperativity in a protein-protein interaction. Structure 2006; 13:1775-87. [PMID: 16338406 PMCID: PMC2746401 DOI: 10.1016/j.str.2005.08.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 08/04/2005] [Accepted: 08/10/2005] [Indexed: 11/29/2022]
Abstract
Although protein-protein interactions are involved in nearly all cellular processes, general rules for describing affinity and selectivity in protein-protein complexes are lacking, primarily because correlations between changes in protein structure and binding energetics have not been well determined. Here, we establish the structural basis of affinity maturation for a protein-protein interaction system that we had previously characterized energetically. This model system exhibits a 1500-fold affinity increase. Also, its affinity maturation is restricted by negative intramolecular cooperativity. With three complex and six unliganded variant X-ray crystal structures, we provide molecular snapshots of protein interface remodeling events that span the breadth of the affinity maturation process and present a comprehensive structural view of affinity maturation. Correlating crystallographically observed structural changes with measured energetic changes reveals molecular bases for affinity maturation, intramolecular cooperativity, and context-dependent binding.
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Affiliation(s)
- Sangwoo Cho
- Center for Advanced Research in Biotechnology W.M. Keck Laboratory for Structural Biology University of Maryland Biotechnology Institute Rockville, Maryland 20850
| | - Chittoor P. Swaminathan
- Center for Advanced Research in Biotechnology W.M. Keck Laboratory for Structural Biology University of Maryland Biotechnology Institute Rockville, Maryland 20850
| | - Jianying Yang
- Center for Advanced Research in Biotechnology W.M. Keck Laboratory for Structural Biology University of Maryland Biotechnology Institute Rockville, Maryland 20850
| | - Melissa C. Kerzic
- Center for Advanced Research in Biotechnology W.M. Keck Laboratory for Structural Biology University of Maryland Biotechnology Institute Rockville, Maryland 20850
| | - Rongjin Guan
- Center for Advanced Research in Biotechnology W.M. Keck Laboratory for Structural Biology University of Maryland Biotechnology Institute Rockville, Maryland 20850
| | - Michele C. Kieke
- Department of Biochemistry University of Illinois Urbana, Illinois 61801
| | - David M. Kranz
- Department of Biochemistry University of Illinois Urbana, Illinois 61801
| | - Roy A. Mariuzza
- Center for Advanced Research in Biotechnology W.M. Keck Laboratory for Structural Biology University of Maryland Biotechnology Institute Rockville, Maryland 20850
| | - Eric J. Sundberg
- Boston Biomedical Research Institute Watertown, Massachusetts 02472
- Correspondence:
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10
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Mnaimneh S, Damaj M, Barhoumi R, Mouneimne Y, Veyret B, Geffard M, Vincendeau P. Circulating antibodies directed against nitrosylated antigens in trypanosome-infected mice. Exp Parasitol 2003; 105:241-7. [PMID: 14990318 DOI: 10.1016/j.exppara.2003.12.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2003] [Revised: 12/12/2003] [Accepted: 12/24/2003] [Indexed: 11/20/2022]
Abstract
Nitric oxide has been implicated as an effector cytotoxic molecule in trypanosomiasis. In this work, we investigated the presence of circulating antibodies directed against nitrosylated epitopes as biological indicators for nitric oxide (NO) production in the sera of trypanosome-infected mice. We tested these sera with synthetic antigens, such as S-nitrosated protein or nitrosylated conjugates of amino acids that possess a high affinity to NO, by an immunoenzymatic assay. We detected antibodies directed against nitroso epitopes in the sera of infected mice, as compared to non-infected control mice. The antibody response was linked to the IgM isotype. Our results indicate the production of NO and its derivatives in trypanosomiasis. This production may potentially induce the synthesis of nitroso epitopes in vivo and favor the development of a humoral immune response.
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Affiliation(s)
- Sanie Mnaimneh
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA.
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11
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Kleinstein SH, Singh JP. Why are there so few key mutant clones? The influence of stochastic selection and blocking on affinity maturation in the germinal center. Int Immunol 2003; 15:871-84. [PMID: 12807826 DOI: 10.1093/intimm/dxg085.sgm] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A small number of key somatic mutations lead to high-affinity binding in the anti-hapten immune responses to 2-phenyl-5-oxazolone (phOx) and (4-hydroxy-3-nitrophenyl)acetyl (NP). Affinity maturation models of the germinal center hold that B cells carrying these key mutations are preferentially selected for expansion within the germinal centers. However, additional factors are required to account for some quantitative aspects of affinity maturation in vivo. Radmacher et al. have shown that key mutants are observed in vivo significantly less frequently than expected by these models. To account for this finding, they propose that selection is a stochastic process where key mutants may be overlooked by positive selection or recruited out of the germinal center. While acknowledging that a minimal amount of stochastic selection is probably unavoidable in the germinal center, we instead propose a structural explanation for this key mutant discrepancy. This model is based on the existence of a large number of blocking mutations whose presence can prevent the ability of key mutations to confer high-affinity binding. Using mathematical modeling and computer simulation, we show that in addition to reconciling the key mutant discrepancy, the blocking model accounts for other aspects of experimental data that are not predicted by the stochastic selection model. In particular, the blocking model is consistent with the observation that key mutants generally exhibit a higher number of mutations per sequence in the phOx response, but a lower number in the NP response.
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Affiliation(s)
- Steven H Kleinstein
- Department of Computer Science, Princeton University, Princeton, NJ 08544, USA.
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12
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Li Y, Li H, Yang F, Smith-Gill SJ, Mariuzza RA. X-ray snapshots of the maturation of an antibody response to a protein antigen. Nat Struct Mol Biol 2003; 10:482-8. [PMID: 12740607 DOI: 10.1038/nsb930] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2002] [Accepted: 04/16/2003] [Indexed: 11/08/2022]
Abstract
The process whereby the immune system generates antibodies of higher affinities during a response to antigen (affinity maturation) is a prototypical example of molecular evolution. Earlier studies have been confined to antibodies specific for small molecules (haptens) rather than for proteins. We compare the structures of four antibodies bound to the same site on hen egg white lysozyme (HEL) at different stages of affinity maturation. These X-ray snapshots reveal that binding is enhanced, not through the formation of additional hydrogen bonds or van der Waals contacts or by an increase in total buried surface, but by burial of increasing amounts of apolar surface at the expense of polar surface, accompanied by improved shape complementarity. The increase in hydrophobic interactions results from highly correlated rearrangements in antibody residues at the interface periphery, adjacent to the central energetic hot spot. This first visualization of the maturation of antibodies to protein provides insights into the evolution of high affinity in other protein-protein interfaces.
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Affiliation(s)
- Yili Li
- Center for Advanced Research in Biotechnology, W.M. Keck Laboratory for Structural Biology, University of Maryland Biotechnology Institute, 9600 Gudelsky Drive, Rockville, Maryland 20850, USA
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13
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Kleinstein SH, Singh JP. Toward quantitative simulation of germinal center dynamics: biological and modeling insights from experimental validation. J Theor Biol 2001; 211:253-75. [PMID: 11444956 DOI: 10.1006/jtbi.2001.2344] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
As models of immune system dynamics are developed, it is important to validate them with specific experimental data in order to understand their shortcomings and guide them toward becoming predictive. In this paper, we examine whether a particular mathematical model of germinal center dynamics, proposed by Oprea and Perelson, can reproduce experimental data from two specific primary responses, namely those directed against the haptens 2-phenyl-5-oxazolone and (4-hydroxy-3-nitrophenyl)acetyl. We develop formulas for estimating response-specific model parameters, as well as constraints for validating the model. In addition, we outline a general methodology for translating a continuous/deterministic model, expressed as a set of ordinary differential equations, into a discrete/stochastic framework. This methodology is used to create a new implementation of the Oprea and Perelson model that enables comparison with data on individual germinal centers. We conclude that while the model can reproduce the average dynamics of splenic germinal centers, it is at best incomplete and does not reproduce the distribution of individual germinal center behaviors. In addition to suggesting possible extensions to the model which can reconcile the dynamics with some aspects of the experimental data, we make a number of specific predictions that can be tested by in vivo experiments to obtain further insights and validation.
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Affiliation(s)
- S H Kleinstein
- Department of Computer Science, Princeton University, 35 Olden Street, Princeton, NJ 08544, USA.
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Liu J, Minnerath JM, Nelson RD, Mueller CM, Jemmerson R. Kinetic and genetic bases for the heteroclitic recognition of mouse cytochrome c by mouse anti-pigeon cytochrome c monoclonal antibodies. Mol Immunol 2000; 37:847-59. [PMID: 11257306 DOI: 10.1016/s0161-5890(01)00003-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The B lymphocyte response to pigeon cytochrome c (CYT) in BALB/c mice was previously shown to initiate as a heteroclitic response specific for the self antigen mouse CYT. As the immune response progressed, the mAb that were produced became less heteroclitic and often bound pigeon CYT with higher affinity than they bound mouse CYT [Minnerath, J. et al., 1995. Proc. Natl. Acad. Sci. USA 92, 12379-12383]. To study the basis for heterocliticity and its loss in this system, the H and L chain amino acid sequences of anti-pigeon CYT mAb obtained from the primary and secondary Ab responses were first compared. The most frequent somatic mutations and Ig gene joints were then introduced into an engineered single-chain Fv (scFv) that expressed the germline-encoded V(H) and V(L) amino acid sequences. The effects of those changes on the on- rate, off-rate, and affinity constants in binding both mouse and pigeon CYT were determined by surface plasmon resonance. In this system, the heterocliticity of primary mAb was largely due to a decreased on-rate constant for binding pigeon CYT relative to mouse CYT. Various combinations of the three frequently occurring H chain somatic mutations (H31, H56, and H58) increased the on-rate constant to maximal levels. Only one of the mutations (H58) decreased the off-rate constant when in combination with the other mutations and the effect of H58 was greater for scFv binding mouse CYT than pigeon CYT. Consequently, the mutated scFv and many secondary mAb remained heteroclitic, although their affinities for pigeon CYT increased. Secondary mAb that were no longer heteroclitic expressed non-canonical amino acid sequences in the V(H)-D-J(H) joint in the context of the canonical V genes or expressed different V genes. In addition to providing insight into the molecular basis for heterocliticity, our findings confirm that both faster on-rate and slower off-rate constants are favored during affinity maturation of the Ab response.
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Affiliation(s)
- J Liu
- Department of Microbiology and Center for Immunology, University of Minnesota Medical School, Box 196 Mayo Building, 420 Delaware St. S.E., Minneapolis, MN 55455, USA
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Abstract
The affinity maturation of antibody 48G7 from its germline predecessor 48G7g has been studied at a molecular level through a combination of structural and biochemical means. Each of the nine somatic mutations accumulated during affinity maturation has been assessed for gain or loss of function in both the germline and affinity-matured antibodies. Individual somatic mutations were found to be either positive or neutral in their effects on affinity for hapten JWJ1, with a marked context-dependence for some sites of mutation. In a number of cases significant cooperativity was found between pairs of somatically mutated residues. Interpretation of the structural changes introduced by many of the point mutations has been possible due to the availability of high-resolution crystal structures of 48G7g and 48G7, and mechanisms by which these structural changes may result in enhanced affinity for hapten have been identified. Precise dissection of structure-function relationships in this system provides additional insights into the role of cooperativity in the evolution of antibody affinity. Comparison of 48G7 with previously characterized systems provides a varied view of the structure-function mechanisms by which the humoral immune system produces large increases in affinity.
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Affiliation(s)
- P L Yang
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
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Saboori AM, Rose NR, Burek CL. Iodination of human thyroglobulin (Tg) alters its immunoreactivity. II. Fine specificity of a monoclonal antibody that recognizes iodinated Tg. Clin Exp Immunol 1998; 113:303-8. [PMID: 9717982 PMCID: PMC1905039 DOI: 10.1046/j.1365-2249.1998.00644.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In a previous investigation, we found that murine MoAb 42C3, raised against human Tg, recognized Tg differently depending upon its level of iodination of Tg. A possible explanation for this finding is that iodine is directly involved with the specific epitope recognized by MoAb 42C3. In the present study, we report that the binding of MoAb 42C3 to iodinated Tg is inhibited by T4, T3, reverse T3 (rT3), triiodothyroacetic acid (triac), diiodothyronine (T2), diiodotyrosine (DIT), but not by thyronine (TO) or tyrosine. The order of inhibition of these iodinated compounds is T4 > T3 > rT3 > triac > T2 > DIT. The MoAb 42C3 does not have the same specificity as the T3, T4-receptor since the order of binding of these iodinated compounds on the receptor differed from the order of their inhibition of this MoAb. Monoclonal antibody 42C3 also recognized non-iodinated Tg that was subsequently iodinated in vitro. It failed to recognize another protein, bovine serum albumin, that was iodinated in vitro by the same method. These results suggest that iodinated tyrosines and thyronines determine the binding specificity of MoAb 42C3. The inhibitory effects of these compounds on MoAb 42C3 depend on their iodine content as well as location of iodine in the aromatic ring.
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Affiliation(s)
- A M Saboori
- Department of Pathology, School of Medicine, The Johns Hopkins University, Baltimore, MD 21205-2196, USA
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